We are building a document rendering tool using them. It’s a pretty large project, and there have been some really good improvements in Clang’s implementation of C++20 modules in the past few versions.
Did you create your own dialect of C++ along the way? I see co_try$(...) and co_trya$(...) whose definitions I can't find, and I assume they're macros that work either with or without coroutines... did you measure the performance overhead with coroutines?